The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Known powertrain systems include engines mechanically coupled to transmission devices to generate and transfer torque to an output member. Known transmission devices include friction clutch packs that transfer torque when activated. Known mechanisms include hydraulically actuated pistons that use hydraulic pressure to apply normal force to a clutch apply plate to engage contiguous clutch plates, thus activating a friction clutch pack to transfer torque. Known engine systems for hybrid powertrain systems use autostop and autostart events to discontinue engine operation during ongoing powertrain operation to conserve fuel. Known powertrain systems use hydraulic pumps to provide pressurized hydraulic fluid to transmission devices to activate and deactivate friction clutch packs to transfer torque. Known hydraulic pumps are mechanically driven by the engine or electrically driven by electric motors. When an engine is shut down in response to an autostop event, a mechanically-driven hydraulic pump is also shut down. It is known to use an electrically-driven auxiliary hydraulic pump to provide hydraulic pressure for clutch activation when an engine is shut down in response to an autostop event. An electrically-driven auxiliary hydraulic pump adds weight, consumes electrical power, requires packaging space, and increases system complexity of a hybrid powertrain system.